We’ve changed out a light fixture. We put in the new fixture, and all was hunky dory. We then took the new fixture down to do some ceiling repair work. When we put the new fixture back up today, it doesn’t work. That is, when wired properly (or what I think is correct), the light stays on all the time. The switch no longer controls it. It wasn’t doing this before, and I can’t figure out what has changed. The fixture worked before with these wires and the switch hasn’t changed.
How many and what color are the wires coming out of the ceiling? It sounds as though there may be three wires–a neutral (white), a switched hot (probably black) and an unswitched hot (possibly red, but could be black also). Either that or by an astounding coincidence, the wall switch fused closed at the same time you replaced the fixture. Another possibility is that the switch was improperly wired in the neutral line instead of the hot. In this case, it’s possible that a wiring fault in the fixture allows the current to find an alternate path through ground, rendering the switch inoperable.
I’m thinking that the most likely case is that the fixture was improperly wired such that the neutral was being switched rather than the hot, and that you’ve now hooked up the neutral in such a way that it’s connected with other unswitched neutrals.
OK, your not going to have two hot wires. You’re going to have a hot, neutral anfdground, usually black, white and green respectively. Q.E.D. is right that the first place to check is for feedback in the ground. Her’s a basic house type diagram. You probably need to remove the fixtiure and determine, w/ a circuit tester, which wire is hot, if two are hot you need to trace back until you find a short somewhere. If you worked on the switch, that may be the problem. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/hsehld.html
Thanks for the thoughts. We’re calling in a professional. It seems to me that it’s a simple matter of math; there are only so many permutations one can try before one’s exhausted the options. Given that there’s a possibility that we’re dealing with a bigger problem than connecting wire A to wire B, I’ll call in the guy with the license and have him determine the problem.
But I appreciate all the input, and I’m glad to hear that it’s not that we missed something obvious.
My bet is that the device box has a hot and neutral supplied to it, and the other black and white pair is a switch leg. The hot coming in to the device box would have been nutted to one side of the switch leg (made constant hot), with the return of the switch leg (switched hot) going to the fixture black. Fixture white would go to the supply/line neutral/white. If the OP inadvertently got some wires crossed, the switch is neatly removed from the equation, and the fixture is connected to line as long as the breaker/fuse is closed.
The rest of the posts in this thread are 10 years old, but here’s the advice they should have given the guy:
If you managed to rewire the light so it’s always on and you can’t figure it out you have no business wiring your light. Call a professional!
Okay, so maybe you just need some good advice and you can fix it yourself. Get a multimeter / voltage meter. Measure the voltage between the black wires and the white wires, with and without the switch to on. Connect the pair, or pairs that are on when the switch is on and off when the switch is off to the light.
See point one of post #13. Ignore point two of said post. Wiring instructions are difficult to parse in print (on both ends). When dealing with an ambiguous problem described by the uninitiated, there is way too much room for error either way.
Any electrician will tell you that you cannot rely on wire colours to determine hot or neutral. This is because you have no idea what the person who originally wired them up was doing. It is quite possible in house electrics for two wrongs to make a right - that is for two errors to cancel each other out.
How many wire nuts did you pull off? Typical modern household wiring runs black and white wires in pairs with the odd red now and then. You can’t have more black than white in a junction box unless one of the black is actually a painted or taped white to signify black. With conduit, all bets are off.
That said this is the correct answer:
Sounds like someone didn’t wire the switch wire into the circuit.
There should be one 2 conductor wire going to the switch. Identifying that wire is step one. You can kill power and check continuity. The switch wire is just a loop through the switch and back to the light.